It is not the same to consume less electrical energy than to strictly use the necessary one. The former requires advanced strategies and the latter simply has to do with care and planning.
By Alfredo Sotolongo*
I never tire of explaining that the easiest thing to do to counteract the increase in the cost of energy is to avoid wasting it; in other words, apply the three basic concepts to conserve energy:
- Preventive maintenance.
- Schedule the use of mechanical and electrical equipment.
- Use equipment and systems to avoid wasting energy.
As we all know, the cost of energy, and especially that of electric power, is projected to increase exponentially over the next five years.
Studies reveal that the high cost of energy is the biggest concern of business managers, particularly hotels, hospitals, industries and office buildings.
By investing in the three basic concepts, in addition to minimizing the waste of energy, several marginal benefits are achieved and not all necessarily economic. It manages to increase the productivity of employees, makes the operation of the company more competitive and also contributes to the ecological benefit of the country.
With new systems and equipment developed in the last five years, there is the possibility of energy savings in many areas of the buildings mentioned above.
The first thing, which is both the simplest and requires minimal investment, should be the preventive maintenance program. Regularly inspect and take corrective action on the following components:
- In boilers, if they have them, verify that the combustion is adjusted to the optimal condition and the fan belt is operating correctly.
- All equipment, such as air conditioning units and fans, must keep the belts and pulleys with the correct fit.
- Change the filters of the air conditioning units when they are saturated to minimize pressure drop.
- Ensure that the coils of the refrigeration and air conditioning units are clean to maximize heat transfer.
- Regularly inspect refrigerant pressures in air conditioning and refrigeration equipment.
I often emphasize air conditioning systems because in our countries, which are totally or partially between the tropics of Cancer and Capricorn, air conditioning represents, depending on the enthalpy of the outside air, between 50% and 70% of electricity consumption.
Operate when strictly necessary
The second basic and also relatively inexpensive concept to implement is to program the start and stop of electrical or mechanical equipment along with the turning on and off of lights. This prevents energy from being consumed in hours that such equipment or lights should not operate, which has always caught my attention when doing energy analysis.
We have found, for example, air conditioning units operating at times when the rooms are unoccupied and not only operating, but maintaining the design temperature.
Our experience shows us that employees don't always remember to turn off equipment or lights. That can only be effectively achieved through programming, using low-cost, easy-to-operate systems.
The third concept that must be analyzed responsibly from the financial point of view, is the application of equipment and systems to recover the energy that is wasted.
For example, in ventilation systems where cold and dehumidified air is extracted to the outside, and can be used to pre-cool and dehumidify the outside air that is introduced into the air conditioning system. Also, apply variable volume of water and air whenever it can be justified, based on the savings and the time of the recovery of the investment.
The central air conditioning plant is where the highest percentage of electrical energy is consumed. It is recommended to design it using variable volume of water, which ensures that the entire plant adapts to the thermal load that occurs at all times and, therefore, the consumption is directly proportional to the thermal load, neither more nor less.
In addition, chillers must be selected with centrifugal compressors to operate at partial loads, between 25% and 80% of their total capacity, which represents the lowest possible consumption of kilowatts per ton of refrigeration.
The company SMARDT is one of the manufacturers that has dedicated the largest percentage of its resources to the research and development of chillers with centrifugal compressors, not only with magnetic bearings, but do not need oil for lubrication. This requires only two amperes of current to start the compressor (compared to other similar chillers that need up to 600 amps to start up). The efficiency is excellent at partial loads and by not needing oil for lubrication, the heat transfer in the evaporator and condenser is maximized.
In future articles, I will delve into these basic concepts to share with you experiences lived in the 45 years of my professional career.
* President of Protec, Inc., is certified as a professional engineer in Puerto Rico and the state of Florida; has more than 40 years of experience in the application and sale of systems and equipment for energy conservation. He is a member of ASME (American Society of Mechanical Engineers), AEE (Association of Energy Engineers), ASHRAE and was president of the Miami chapter of that association.
